Problem: $ { \left[\begin{array}{rrr}{-2} & {-1} & {4} \\ {1} & {2} & {1}\end{array}\right]-\left[\begin{array}{rrr}{2} & {-1} & {1} \\ {2} & {1} & {4}\end{array}\right] = {?} } $
Solution: To find the difference of two matrices, subtract the corresponding items between each matrix. ${\left[\begin{array}{rrr}{-2}-{2} & {-1}-{-1} & {4}-{1} \\ {1}-{2} & {2}-{1} & {1}-{4}\end{array}\right]}$ Now, simplify: ${\left[\begin{array}{rrr}{-4} & {0} & {3} \\ {-1} & {1} & {-3}\end{array}\right]}$